Inhibition of pyrophoric iron sulfide activity

ABSTRACT

Methods for inhibiting pyrophoric iron sulfide activity are disclosed. Methods are disclosed for inhibiting the sulfidation of iron oxides to iron sulfides and/or the oxidation of iron sulfide to inhibit pyrophoric activity. The methods comprise contacting iron oxides and/or iron sulfide with a liquid, solution, aerosol, or gaseous inhibitor comprising alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides, oximes; sulfur-containing compounds and phosphorus-containing compounds.

FIELD OF THE INVENTION

The present invention relates to compositions for and methods of inhibiting pyrophoric activity of iron sulfide. More particularly, the present invention relates to compositions for and methods of inhibiting the formation of pyrophoric iron sulfide by inhibiting the sulfidation of iron oxides and/or inhibiting the oxidation of iron sulfide.

BACKGROUND OF THE INVENTION

Corrosion of iron by air yields rust, or iron oxides such as goethite (∝-FeO (OH)), hematite (Fe₂O₃) and magnetite (Fe₃O₄). Exposure of these iron oxides to hydrogen sulfide rich conditions where oxygen content is low results in a sulfidation reaction which yields mackinawite (FeS_(x)) which can form greigite (Fe₃S₄) and/or pyrite (FeS₂). This sulfidation step is exothermic. Oxidation of these iron sulfides, as by exposures to air or oxygen rich conditions, is highly exothermic and can result in pyrophoric activity.

Hydrogen sulfide is often present in crude oil and can react with iron oxides formed in transportation, processing or storage vessels. Exposure of the resulting iron sulfides to air can result in pyrophoric activity and a potentially explosive situation. For example, the reaction of hydrogen sulfide with iron oxides present in oil tankers in the area above the liquid crude oil can result in the formation of pyrophoric iron sulfides. Upon discharge of the crude oil, exposure of the iron sulfides to air can result in pyrophoric activity in the head space and explosive results are possible. Similar conditions can exist in other crude oil handling, transporting or processing vessels. In particular, pyrophoric iron sulfides have been found in refinery units, sour water strippers and amine units in addition to oil tankers. These units have reducing atmospheres. When these units are opened up, as for repair or maintenance, exposure to air gives rise to the possibility for the pyrophoric iron sulfides to ignite flammable vapors that are still in the units.

The reactions involved in the formation of iron sulfide and its subsequent oxidation on exposure to oxygen may be represented in a simplified form as follows:

Sulfidation Reaction

Fe₂O₃+3 H₂S→2 FeS+S+3H₂O

Oxidation Reaction

4 FeS+3 O₂→2 Fe₂O₃+4 S

Both of these reactions are exothermic with enthalpy, ΔH, values of −168 and −635 kJ/mol, respectively. If the oxidation reaction is allowed to proceed rapidly with little dissipation of heat, high temperatures leading to glowing and sparking can be expected in the material.

Russian Patent No. 1,449,138 discloses the use of polymer/ionomers containing amide and carboxylate groups to prevent the spontaneous combustion of pyrophoric deposits of iron sulfide. The disclosed method comprises contacting pyrophoric deposits of iron sulfide with an aqueous solution of a deactivating solution of a polymer-ionomer containing amide and carboxylate groups.

SUMMARY OF THE INVENTION

The present inventors have discovered compositions for and methods of inhibiting pyrophoric iron sulfide activity. The compositions and methods of the present invention can inhibit the sulfidation of iron oxide to iron sulfides and/or the oxidation of iron sulfide. The methods of the present invention comprise contacting iron oxides and/or iron sulfide with a liquid, solution, or gaseous inhibitor comprising alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorus-containing compounds. The treatments of the present invention inhibit either the sulfidation and/or the oxidation reactions which can result in the formation and/or pyrophoric activity of iron sulfide.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a method for inhibiting the formation of pyrophoric iron sulfide and/or precusors thereof in the production, transportation and/or storage of petroleum products which contain hydrogen sulfide. The methods of the present invention comprise inhibiting the formation of pyrophoric iron sulfide by inhibiting the sulfidation of iron oxide to yield iron sulfides and/or the oxidation of iron sulfides by contacting the iron oxide or iron sulfide with a liquid, solution, gaseous or aerosol treatment. The treatment comprises alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorus-containing compounds. The amines useful in the methods of the present invention are preferably alkylamines or arylamines which have a boiling point above the temperature of the pyrophoric iron sulfide at the time of treatment, this temperature can vary from ambient temperature up. The preferred oxygen containing compounds are selected from alcohols, aldehydes, esters, acids and ketones preferably having boiling points of greater than about 170° C.

The pyrophoric nature of iron sulfide is well known. The formation of pyrophoric iron sulfide in the vapor areas of oil tankers and refinery units such as sour water strippers and amine scrubbers is considered to be the product of the reaction of hydrogen sulfide present in the hydrocarbon with rust formed by corrosion on the inner surfaces of the steel tanks or equipment. Aging of the materials sometimes increases the tendency of the pyrophoric behavior. At temperatures of 75 to 100° C. sparking can occur as soon as the sulfides are exposed to air

The present inventors discovered that the pyrophoric action of iron sulfide and/or precursors thereof can be inhibited by application of solutions, liquid compounds, aerosols, or vapors to iron sulfide solids. The use of vapor or aerosol application is desirable in liquid storage tanks where the iron sulfide can be formed in the areas above the hydrocarbon liquid.

The treatment compounds of the present invention can inhibit the sulfidation step or the oxidation step leading to pyrophoric activity of iron sulfides.

It is theorized that the treatments form coordinate bonds to the iron atom of the oxides or sulfides through the heteroatom of the treatment. When such a bond breaks, if the treatment compound has a high vapor pressure, it will evaporate, leaving an active iron atom. Such coordinate bonds are strongest for trisubstituted nitrogen compounds such as amines, less strong for nitrites and oxygen-containing compounds. While this theory is believed to be accurate, it is not intended to be limiting with respect to the scope of the present invention.

The treatment compounds of the present invention can include nitrogen-containing compounds such as alkylamines, arylamines, imines; oxygen-containing compounds such as alcohols, aldehydes, esters, acids and ketones; mixed nitrogen-containing and oxygen-containing compounds such as alkanolamines, non-polymeric amides, hydroxylamines, Mannich products, polyisobutylenesuccinimides (PIBSIs), oximes; sulfur-containing compounds and phosphorous-containing compounds.

Examples of alkylamines are n-propylamine, iso-propylamine, n-butylamine, iso-butylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, n-decylamine, stearylamine, oleylamine, diethylamine, di-n-propylamine, di-iso-propylamine, di-n-butylamine, di-iso-butylamine, di-sec-butylamine, di-tert-butylamine, di-n-pentylamine, di-n-hexylamine, di-n-heptylamine, di-n-octylamine, di-n-nonylamine, di-n-decylamine, distearylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tri-tert-butylamine, tri-n-pentylamine, tri-n-hexylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decylamine, tristearylamine, cyclohexylamine, N-methylcyclohexylamine, N,N-dimethylcyclohexylamine, cyclopentyl-amine, ethylenediamine, diethylenetriamine, triethylenetertamine, tetraethylenepentamine, tetramethylethylenediamine, 1,2-propylene-diamine, 1,3-propylenediamine, polyethylenamine, benzylamine, phenethylamine, geranylamine, imidazolines, 3-methoxypropylamine, N-(2-aminoethyl)piperazine, tert-amyl-tert-octylamine, 1-adamantanamine.

Examples of arylamines are aniline, N-methylaniline, N,N-dimethylaniline, N-ethylaniline, N,N-diethylaniline, 2-methylaniline, 3-methylaniline, 4-methylaniline, 2-ethylaniline, 3-ethylaniline, 4-ethylaniline, pyridine, 2-aminopyridine, quinoline, isoquinoline, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, N,N′-bis-(sec-butyl)-p-phenylenediamine, N,N′-dimethyl-p-phenylene-diamine, N-methyl-p-phenylenediamine.

Examples of imines are N,N′-bis(salicylidene)-1,6-hexanediamine, N,N′-bis(salicylidene)-1,4-butanediamine, N,N′-bis(salicylidene)-1,3-propanediamine, N,N′-bis(salicylidene)ethylenediamine.

Examples of nitriles are cis-2-pentenenitrile, 2-pyridylacetonitrile, benzonitrile, 3-anilinopropionitrile, cinnamonitrile, adiponitrile, phenyleneacetonitrile, heptanenitrile, p-tolunitrile.

Examples of alcohols are ethanol, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, cyclopentanol, cyclohexanol, ethylene glycol, diethylene glycol, triethylene glycol, catechol, tert-butylcatechol, phenol, 2-methylphenol, 3-methylphenol, 4-methylphenol, 1,5-pentanediol, phenol, o-cresol, m-cresol, p-cresol, eugenol, 1,9-nonanediol, 1-naphthol, 2-methylcyclohexanol, isoborneol, benzyl alcohol, cholesterol, 1,4-butanediol, pentaerythritol, oleyl alcohol, poly(vinyl alcohol), cis-1,2-cyclopentanediol.

Examples of aldehydes are octanal, butanal, pentanal, hexanal, heptanal, nonanal, decanal, 2-ethylhexanal, benzaldehyde, p-anisaldehyde, 2-hydroxy-5-methylbenzaldehyde, glyceraldehyde, p-tolualdehyde, salicylaldehyde.

Examples of ketones are acetone, 2-butanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, 4-methyl-2-pentanone, 3-methyl-2-pentanone, cyclopentanone, cyclohexanone, acetophenone, 2′-methyl-acetophenone, 3′-methyl-acetophenone, 4′-methyl-acetophenone, benzophenone, benzylacetone, 2′-hydroxyacetophenone, 9-fluorenone.

Examples of carboxylic acids are acetic acid, propanoic acid, butanoic acid, isobutyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, 3-methyladipic acid, stearic acid, oleic acid, eicosanoic acid, lactic acid, glycolic acid, malic acid, succinic acid, maleic acid, benzoic acid, salicylic acid, trimethyl-acetic acid, thiosalicylic acid, thiolactic acid, thiodiglycolic acid, 2-pyridinecarboxylic acid, mercaptoacetic acid.

Examples of esters are ethyl acetoacetate, methyl lactate.

Examples of alkanolamines are monoethanolamine, diethanolamine, triethanolamine, N-methylmonoethanolamine, N,N-dimethylmonoethanolamine, N-methyidiethanolamine, N-ethyidiethanolamine, N,N-diethylethanolamine, N-propyidiethanol-amine, N-octyidiethanolamine, monopropanolamine, dipropanolamine, tripropanolamine, 8-hydroxyquinoline, 2-aminophenol.

Examples of non-polymeric amides are N,N-dimethylformamide, o-toluamide, succinamide, acetamide, benzamide, formamide, N,N-dimethylacetamide, N-ethylacetamide.

Examples of hydroxylamines are N,N-diethylhydroxylamine (DEHA), N,N-di-n-propylhydroxylamine, N,N-di-iso-propylhydroxylamine, N,N-bis-(2-hydroxypropyl)hydroxylamine, N-ethylhydroxylamine, N,N-dibenzylhydroxylamine, N-benzylhydroxylamine.

Examples of Mannich products are reaction products of phenol or alkylphenols with an aldehyde and an amine as for example exemplified in U.S. Pat. No. 4,749,468 incorporated herein by reference.

Examples of polyisobutylenesuccinimides (PIBSIs) are reaction products of polyisobutylenesuccinic anhydride with primary amine compounds and preferably polyalkyeneamines with at least one primary amine. The polyisobutylene portion of the molecule could also be any other alkyl or polyalkylene such as methyl, butyl, cyclohexyl, polyethylene, or polypropylene.

Examples of oximes are acetone oxime, cyclopentanone oxime, cyclohexanone oxime, dimethylglyoxime, 2-pyridinealdoxime, 1,2-cyclohexanedione dioxime, 2-indanone oxime, 2-heptanone oxime, 4-methyl-2-pentanone oxime, salicylaldoxime, 1-phenyl-1,2-propanedione 2-oxime, benzaldehyde oxime.

Examples of phosphorous compounds are triethyl phosphite, dibenzyl phosphite, triphenyl phosphite, triphenylphosphine oxide, triphenylphosphine, triisodecyl phosphite, isooctyl diphenyl phosphite, triphenyl phosphate.

Examples of sulfur compounds are 2,3-toluenedithiol, sulfolane, 2-aminothiophenol, butyl sulfoxide, butyl sulfone, p-tolyl sulfone, benzyl sulfone, 2-mercaptoethanol.

Preferred treatment compounds include but are not limited to iso-butylamine, n-propylamine, diethylamine, ethanol, octanal, t-butylcatechol (TBC), triethylene glycol (TEG), ethylene glycol, triethylenetetramine (TETA), N,N′-bis-(sec-butyl) -p-phenylenediamine, dimethylformamide (DMF), triethyl phosphite (TEP), quinoline, imidazoline, tetramethylethylenediamine (TMEDA), cis-2-pentenenitrille, polyisobutylenesuccinimide (PIBSI), acetone oxime, acetone, acetic acid, propanoic acid, ethyl acetoacetate, cyclohexanone, the Mannich product of p-nonylphenol/ethylenediamine (EDA)/formaldehyde at a molar ratio of 2/1/2.

The treatment compounds can be added to the iron oxides or pyrophoric iron sulfides in neat form or as a solution when dissolved in a solvent. The solvent can be water or any suitable organic solvent, such as heavy aromatic naphtha.

The treatment compound should have a boiling point above the temperature of the iron oxides or pyrophoric iron sulfides when the treatment compound is applied. Preferably the temperature difference between the boiling point of the treatment and the treatment temperature is about 30° C. for oxides and about 50° C. for sulfides.

Enough treatment compound is added to retard the sulfidation or oxidation reaction. That means approximately a chemical equivalent amount of treatment compound, based on active heteroatoms, to iron compound. Depending on the particle size of the iron compound, less than equivalent amounts of treatment compound may be needed, because only surface iron atoms should be immediately active.

EXAMPLES

The present invention will now be further described with reference to a number of specific examples which are to be regarded as illustrative, and not as restricting the scope of the invention.

The effect of treatment compounds on the pyrophoric activity of iron sulfide was studied in an apparatus which comprised a fritted glass funnel fitted with a filter paper to prevent iron oxide (5.5 g, 34 mmol) from clogging the frit. The bottom of the funnel was fitted with a two-way valve which allowed connection to a hydrogen sulfide generator or a vacuum pump. The top of the funnel was sealed with a rubber stopper fitted with a thermocouple that was placed in the iron oxide material in the funnel and a glass tube connected to a three-way valve. The three-way valve was connected to an exit line to a hydrogen sulfide caustic scrubber, a line for argon purge and a burette. The hydrogen sulfide generator consisted of a three-necked round bottom flask in which sulfuric acid (50 mL of 20%) was added at a rate of 8.8 mL/min by means of a syringe pump to Na₂S. 9H₂O (30 g, 125 mmol) dissolved in deionized water (25 mL). The three-necked flask was equipped with a magnetic stirrer and three septum caps. In the septum caps were placed a needle for sulfuric acid delivery, a needle for argon or air purging and an exit tube to carry the hydrogen sulfide gas to the fritted glass funnel. Argon was purged through the entire apparatus for 30 minutes at a rate of 330 mL/min. Hydrogen sulfide gas was carried by argon purge to the iron oxide material which was in the fritted glass funnel which turned to black pyrophoric iron sulfide and produced a temperature of between 120 and 200° F. After the temperature returned to ambient, the treatment to be tested was placed in the burette and added to the funnel under slight vacuum. After about ten seconds the treatment liquid was drawn off with a vacuum. Fifteen milliliters of pentane or acetone was added by means of the burette to wash off excess treatment liquid and the funnel placed under vacuum for five to fifteen minutes. Alternatively, the treatment was placed in the flask as a vapor by first flushing with argon and thereafter passing argon over the treatment to vaporize it and transport it on to the iron sulfide. Air was then added to the apparatus and any temperature change and color changes noted.

Treatment procedure A employed the above apparatus and involved contacting the iron oxide with hydrogen sulfide prior to application of the treatment compound. Treatment procedure A was a determination of the effect of the treatment compound on the oxidation reaction. Treatment procedure B employed the above apparatus and involved application of the treatment compound prior to contacting the iron oxide with hydrogen sulfide. Treatment procedure B was a determination of the effect of the treatment compound on the sulfidation reaction.

Example 1

A series of temperature measurements were taken with the above described apparatus without the addition of any treatment compound in order to establish a baseline for the temperatures of the sulfidation and oxidation steps for hematite, magnetite and goethite. Table 1 summarizes the data.

TABLE 1 Untreated Runs for Hematite, Fe₂O₃(<100 Mesh); Magnetite, Fe₃O₄(<325 mesh); and Goethite, FeO(OH) (30-50 mesh) Procedure A Sulfidation Oxidation Iron Oxide Temperature (° C.) Temperature (° C.) Hematite 53 254 Hematite 53 274 Hematite 56 324 Hematite 59 119 Hematite 63 354 Hematite 71 324 Hematite 96 135 Hematite 99 268 Hematite 71 207 Hematite 75 141 Hematite 51  46 Hematite 63 157 Hematite 51 305 Hematite 57 404 Hematite 49 326 Hematite 53 216 Average 64 ± 15 241 ± 100 Magnetite 59 206 Magnetite 57 198 Magnetite 53 119 Magnetite 36 293 Magnetite 46 425 Magnetite 48 297 Magnetite 30 245 Average 47 ± 11 255 ± 97  Goethite 51  97 Goethite 54 149 Goethite 28 257 Goethite 62 137 Average 49 ± 15 160 ± 68 

The oxidation temperature for hematite can be seen to be about 241° C., with all but one run being above 119° C. Thus, for treated reactions to be considered successful, temperatures would have to be less than about 50° C. and preferably below about 38° C. With magnetite or goethite, the temperature of the sulfidation step was not as large as with hematite, however, the oxidation temperatures were as large showing that if dry iron oxide exists, hydrogen sulfide vapors can form pyrophoric iron sulfide.

Example 2

Nitrogen compounds were added, as a vapor, to pyrophoric iron sulfide prepared from hematite (Fe₂O₃), in accordance with procedure A described above. Table 2 summarizes the result.

TABLE 2 Treatment Compounds Added as Vapor to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A TREATMENT bp Sulfidation Oxidation (10 mL) (° C.) Temperature (° C.) Temperature (° C.) NH4OH (50 mL) — 61 304 iso-butylamine 68 77  74

Table 2 shows that the vapor phase application of amine, iso-butylamine, retarded the oxidation step. Ammonia did not provide retardation, indicating that higher boiling point amines will retard pyrophoric iron sulfide by vapor phase application.

Example 3

The treatment compounds listed below in Table 3 were added as a vapor to hematite (Fe₂O₃), according to procedure B described above. Table 3 summarizes the results.

TABLE 3 Compounds Added as Vapors to Hematite, Fe₂O₃, Before Adding Hydrogen Sulfide Procedure B TREATMENT bp Sulfidation Oxidation (10 mL) (° C.) Temperature (° C.) Temperature (° C.) n-propylamine 48 27 36 iso-butylamine 68 24 39 diethylamine 55 28 45 trimethylamine  3 33 233  acetonitrile 82 31 117  ethanol 78 26 45 acetone 56 27 57

Example 4

The treatment compounds listed below in Table 4 were added, as a vapor, to magnetite (Fe₃O₄) according to procedure B described above. Table 4 summarizes the results.

TABLE 4 Compounds Added as Vapors to Magnetite, Fe₃O₄, Before Adding Hydrogen Sulfide Procedure B TREATMENT bp Sulfidation Oxidation (10 mL) (° C.) Temperature (° C.) Temperature (° C.) iso-butylamine 68 24  37 acetone 56 31 185 ammonium — 38  94 hydroxide ammonia −33   35 121

Example 5

Iso-butylamine was added, as a vapor, to goethite (FeO(OH)) according to procedures A and B described above. Table 5 describes the results.

TABLE 5 Compounds Added as Vapors to Goethite, FeO(OH) TREATMENT Pro- bp Sulfidation Oxidation Temp- (10 mL) cedure (° C.) Temperature (° C.) erature (° C.) iso-butylamine A 68 53 29 iso-butylamine B 68 61, 61 42, 47

The data in Tables 2-5 show that amines with boiling points of about 48° C. and higher, ethanol and acetone retarded the sulfidation of the iron oxides and/or the oxidation of iron sulfides. While a high boiling point treatment compound is needed, a treatment compound with too low of a vapor pressure may not yield sufficient vapors to retard the iron oxide or sulfide deposit. Therefore, the choice of treatment depends on such factors as temperature, pressure, volume, and amount of iron compounds.

Example 6

The treatment compounds listed below in Table 6 were added as a liquid to hematite (Fe₂O₃) according to procedure B described above. Table 6 summarizes the results.

TABLE 6 Compounds Added to Hematite, Fe₂O₃, Before Adding Hydrogen Sulfide Procedure B Solvent TREATMENT bp Washing Sulfidation Oxidation (10 mL) (° C.) (15 mL) Temp (° C.) Temp (° C.) Pentane^(a) 36 none 77 382  TETA 266 Pentane 28 27 TETA/tetrahydrofuran 266 THF^(c) 27, 27, 28 32, 29, 47 (THF^(b)) N,N′-bis-(sec-butyl)- ˜250 Pentane^(e) 30 40 p-phenylenediamine^(d) Mannich product^(f) ˜350 THF^(c) 28 28 /THF^(b) N,N- 153 Pentane 30 28 dimethylformamide (DMF) N,N- 125 Pentane 69 66 diethylhydroxylamine (DEHA) Acetic acid 118 Pentane 25 28 Ethanol 78 Acetone 27 31 TEG 288 Pentane 31 30 Butyl acetate 124 Pentane 33 83 Water/ethanol^(g) 100 acetone 28 31 Water/ethanol^(h) 100 acetone 26 29 Water/Aliquat 336^(i) 100 Acetone 27 29 TEP 156 Pentane 24 32 ^(a)15 mL used ^(b)10/15 mL used ^(c)25 mL used ^(d)25% active in heavy aromatic naphtha (HAN) ^(e)45 mL used ^(f)Mannich product of p-nonylphenol/ethylenediamine (EDA)/formaldehyde in molar ratio of 2/1/2; 25% active in heavy aromatic naphtha (HAN) ^(g)4/1 mL used ^(h)2.5/2.5 mL used ^(i)10/2 mL used

Example 7

The treatment compounds listed below in Table 7 were added, as a liquid, to magnetite (Fe₃O₄) according to procedure B described above. Table 7 summarizes the results.

TABLE 7 Compounds Added to Magnetite, Fe₃O₄, Before Adding Hydrogen Sulfide Procedure B Solvent Sulfidation Oxidation TREATMENT bp Washing Temperature Temperature (10 mL) (° C.) (15 mL) (° C.) (° C.) DMF 153 Pentane 37 36 DEHA 125 Pentane 28 33 TETA 266 Pentane 31, 26 32, 26

Example 8

The treatment compounds listed below in Table 8 were added, as a liquid, to goethite (FeO(OH)) according to procedure B described above. Table 8 summarizes the results.

TABLE 8 Compounds Added as Liquids with a pentane wash to Goethite, FeO(OH) Sulfidation Oxidation TREATMENT bp Temperature Temperature (10 mL) Procedure (° C.) (° C.) (° C.) TETA B 266 38 32

The data in Tables 6-8 show that the sulfidation step is retarded with liquid treatments containing amines, Mannich products, carboxylic acids, alcohols, hydroxylamines, non-polymeric amides, esters, and phosphites.

Example 9

The treatment compounds listed below in Table 9 were added, as a liquid, to hematite (Fe₂O₃) according to procedure A described above. Table 9 summarizes the results.

TABLE 9 Treatment Compounds Added to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A Sulfi- Oxida- dation tion Wash Temper- Vacuum Temper- TREATMENT bp Solvent ature Time ature (10 mL) (° C.) (15 mL) (° C.) (min) (° C.) aniline 184 pentane 57 15  32 iso-butylamine 68 acetone 57 15  64 iso-butylamine 68 pentane 53 15  39 fatty acid imidazoline ˜290 acetone 58, 61 15 34, 33 fatty acid imidazoline^(a) ˜290 none 85 5  37 fatty acid imidazoline^(a) ˜290 pentane 88 10  54 quinoline 237 acetone 69 15  31 TETA 266 pentane 60, 66 5 36, 28 TMEDA 120 acetone 70 15  33 N,N′-bis-(sec-butyl)-p- ˜250 pentane 66, 53 15 32, 29 phenylenediamine N,N′-bis-(sec-butyl)-p- ˜250 pentane 64 5 383 phenylenediamine^(b) acetonitrile 82 pentane 66, 66 15 234, 234 cis-2-pentenenitrile 127 acetone 71 15  34 ^(a)Dissolved in 15 mL of pentane ^(b)25% active in heavy aromatic naphtha (HAN)

Example 10

The treatment compounds listed below in Table 10 were added, as a liquid, to hematite (Fe₂O₃) according to procedure A described above. Table 10 summarizes the results.

TABLE 10 Treatment Compounds Added to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A Wash Sulfidation Vacuum Oxidation TREATMENT bp Solvent Temperature Time Temperature (10 mL) (° C.) (15 mL) (° C.) (min) (° C.) DMF 153 pentane 68, 83 5 34, 49 Mannich ˜350 acetone 61 15  49 product^(a) Mannich ˜350 pentane 61 5  31 product^(a) Mannich ˜350 pentane 79 5  29 product^(b) PIBSI^(c) ˜390 acetone 66 15  24 PIBSI^(c,d) ˜390 pentane 89 5  43 DEHA 125 acetone 71, 66 15 138, 313 DEHA 125 pentane 52 15 382 nitrobenzene 210 acetone 70 15 202 nitrobenzene 210 pentane 51 15  87 acetone 135 acetone 51 15  32 oxime^(e) ^(a)Mannich product of p-nonylphenol/ethylenediamine (EDA)/formaldehyde in molar ratio of 2/1/2; 25% active in heavy aromatic naphtha (HAN) ^(b)Mannich product of p-nonylphenol/ethylenediamine (EDA)/formaldehyde in molar ratio of 2/1/2; 35% active in heavy aromatic naphtha (HAN) ^(c)Polyisobutylenesuccinimide, MW ˜1500, DETA used in imide ^(d)Dissolved in 15 mL of pentane ^(e)Dissolved in 10 mL of acetone

Example 11

The treatment compound listed below in Table 11 was added, as a liquid, to magnetite (Fe₃O₄) according to procedure A described above.

TABLE 11 Compounds Added to Pyrophoric Iron Sulfide Prepared from Magnetite, Fe₃O₄ (<325 mesh) Procedure A TREAT- MENT bp Wash Solvent Sulfidation Oxidation (10 mL) (° C.) (15 mL) Temperature (° C.) Temp (° C.) TETA 266 pentane 70 33

Example 12

The treatment compound listed below in Table 12 was added, as a liquid, to goethite (FeO(OH)) according to procedure A described above. Table 12 summarizes the results.

TABLE 12 Compounds Added as Liquids with a pentane wash to Goethite, FeO(OH) Oxidation TREATMENT bp Sulfidation Temperature (10 mL) Procedure (° C.) Temperature (° C.) (° C.) TETA A 266 70 31

The data in Tables 9-12 show that liquid, nitrogen-containing treatments of amines, selected nitrites, amides, imides, Mannich products, and oximes retard the oxidation of pyrophoric iron.

Example 13

The treatment compounds listed below in Table 13 were added, as a liquid, to hematite (Fe₂O₃) according to procedure A described above. Table 13 summarizes the results.

TABLE 13 Treatment Compounds Added to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A Wash Sulfidation Vacuum Oxidation TREATMENT bp Solvent Temperature Time Temperature (10 mL) (° C.) (15 mL) (° C.) (min) (° C.) acetic acid 118 pentane 85 5  92 propanoic acid 141 acetone 64 15  77 ethanol 78 pentane 66, 82 5 76, 56 ethylene glycol 197 acetone 65 15  49 TBC 285 acetone 63 15  48 TEG 288 acetone 64 15  28 TEG 288 pentane 68, 71 5 31, 30 acetaldehyde 20 pentane 63 5 350 octanal 171 acetone 57 15  34 butyl acetate 124 acetone 78, 66 15 208, 208 butyl acetate 124 pentane 66 15 262 ethyl 181 pentane 91 5  59 acetoacetate monoglyme 83 acetone 57 15 454 monoglyme 83 pentane 53 15 360 THF 66 none 71 5 311 THF 66 pentane 74 5 274 acetone 56 none 61 15 304 acetone 56 none 67 5  66 acetone 56 none 88 0  54 acetone 56 pentane 72, 74, 77 5 346, 282, 316 cyclohexanone 156 pentane 79 5  81 2,4- 139 acetone 57 15 382 pentanedione 2,4- 139 pentane 76 15 456 pentanedione water 100 acetone 72 15  78

Example 14

The treatment compound listed below in Table 14 was added, as a liquid, to magnetite (Fe₃O₄) according to procedure A described above. Table 14 summarizes the results.

TABLE 14 Compounds Added to Pyrophoric Iron Sulfide Prepared from Magnetite, Fe₃O₄ (<325 mesh) Procedure A Wash TREATMENT bp Solvent Sulfidation Oxidation (10 mL) (° C.) (15 mL) Temperature (° C.) Temp (° C.) TEG 288 pentane 54 33

Example 15

The treatment compounds listed below in Table 15 were added, as a liquid, to hematite, Fe₂O₃, according to procedure A described above. Table 15 summarizes the results.

TABLE 15 Phosphorous Compounds Added to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A Wash Sulfidation Vacuum Oxidation TREATMENT bp Solvent Temperature Time Temperature (10 mL) (° C.) (15 mL) (° C.) (min) (° C.) triphenyl- 377 acetone 71 15 78 phosphine^(a) tributyl phosphite ˜260 acetone 69 15 377 tributyl phosphite ˜260 pentane 74 15 126 ^(a)Dissolved 5 g in 10 mL of acetone

Example 16

The treatment compounds listed below in Table 16 were added, as a liquid, to hematite, Fe₂O3, according to procedure A described above. Table 16 summarizes the results.

TABLE 16 Sulfur Compounds Added to Pyrophoric Iron Sulfide Prepared from Hematite, Fe₂O₃ Procedure A Wash Sulfidation Vacuum Oxidation TREATMENT bp Solvent Temperature Time Temperature (10 mL) (° C.) (15 mL) (° C.) (min) (° C.) 1,2-ethanedithiol^(a) 144 pentane 79 5 104 1,2-ethanedithiol 144 pentane 73 5 421 2,3-toluenedithiol ˜260 acetone 71 15 31 sulfolane 287 acetone 49 15 191 sulfolane 287 pentane 66 15 30 ^(a)Used 2 mL

The data in Tables 13-16 show that selected liquid, oxygen-containing treatments of acids, alcohols, aldehydes, ketones, esters, phosphorus compounds and sulfur compounds retard the oxidation of pyrophoric iron sulfides and/or sulfidation of iron oxides.

While this invention has been described with respect to particular embodiments thereof, it is apparent that numerous other forms and modifications of this invention will be obvious to those skilled in the art. The appended claims and this invention generally should be construed to cover all such obvious forms and modifications which are within the true spirit and scope of the present invention. 

What is claimed is:
 1. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides and/or precursors thereof in the presence of air with an effective inhibiting amount of a treatment compound to inhibit pyrophoric activity of the iron sulfides, said compound being amine, alcohol, ketone, or mixtures thereof.
 2. The method of claim 1 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 3. The method of claim 1 wherein said treatment compound is in a liquid state.
 4. The method of claim 1 wherein the treatment compound being alcohol, ketone, or mixtures thereof, and wherein the iron sulfides and/or precursors are present on an inner surface of steel equipment.
 5. The method of claim 4 wherein said treatment compound is in a liquid state.
 6. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron oxides in the presence of air with an effective inhibiting amount of a treatment compound to inhibit pyrophoric activity of the iron sulfides, said compounds being amine, Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, carboxylic acid, alcohol, nonpolymeric amide, ester, phosphite, or mixtures thereof.
 7. The method of claim 6 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 8. The method of claim 6 wherein said treatment compound is in a liquid state.
 9. The method of claim 6 wherein said treatment compound is a solution.
 10. The method of claim 6, wherein the treatment compound being Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, carboxylic acid, alcohol, nonpolymeric amide, ester, phosphite, or mixtures thereof, and wherein the iron oxides are present on an inner surface of steel equipment.
 11. The method of claim 10 wherein said treatment compound is in a liquid state.
 12. The method of claim 10 wherein said treatment compound is a solution.
 13. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides in the presence of air with an effective inhibiting amount of a treatment compound to inhibit pyrophoric activity of the iron sulfides, said compound being amine, nonpolymeric amide, nitrile, imide, Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, oxime, or mixtures thereof.
 14. The method of claim 13 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 15. The method of claim 13 wherein said treatment compound is in a liquid state.
 16. The method of claim 13 wherein said treatment compound is a solution.
 17. The method of claim 13, wherein the treatment compound being nitrile, Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, oxime, or mixtures thereof, and wherein the iron sulfides are present on an inner surface of steel equipment.
 18. The method of claim 17 wherein said treatment compound is in a liquid state.
 19. The method of claim 18 wherein said treatment compound is a solution.
 20. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides and/or precursors thereof in the presence of air with an effective inhibiting amount of a treatment compound to inhibit pyrophoric activity of the iron sulfides, said compound being carboxylic acid, alcohol, aldehyde, ketone, ester, phosphate, phosphite, thallus, sulfolane, or mixtures thereof.
 21. The method of claim 20 wherein said treatment compound is in a liquid state.
 22. The method of claim 20 wherein said treatment compound is a solution.
 23. The method of claim 20, wherein the treatment compound being carboxylic acid, alcohol, aldehyde, ketone, ester, phosphate, phosphite, thallus, sulfolane, or mixtures thereof, and wherein the iron sulfides and/or precursors are present on an inner surface of steel equipment.
 24. The method of claim 23 wherein said treatment compound is in a liquid state.
 25. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron oxides with an effective inhibiting amount of a treatment compound in an aerosol or in a gaseous state to inhibit pyrophoric activity of the iron sulfides, said compound being amine, Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, carboxylic acid, alcohol, nonpolymeric amide, ester, phosphite, or mixtures thereof.
 26. The method of claim 25 wherein the treatment compound is in an aerosol.
 27. The method of claim 26 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 28. The method of claim 25 wherein the treatment compound is in a gaseous state.
 29. The method of claim 28 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 30. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides with an effective inhibiting amount of a treatment compound in an aerosol or in a gaseous state to inhibit pyrophoric activity of the iron sulfides, said compound being amine, nonpolymeric amide, nitrile, imide, Mannich reaction products of phenol or alkylphenol with an aldehyde and an amine, oxime, or mixtures thereof.
 31. The method of claim 30 wherein the treatment compound is in an aerosol.
 32. The method of claim 31 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 33. The method of claim 30 wherein the treatment compound is in a gaseous state.
 34. The method of claim 30 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 35. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides and/or precursors thereof with an effective inhibiting amount of a treatment compound in an aerosol or in a gaseous state to inhibit pyrophoric activity of the iron sulfides, said compound being carboxylic acid, alcohol, aldehyde, ketone, ester, phosphate, phosphite, thallus, sulfolane, or mixtures thereof.
 36. The method of claim 35 wherein the treatment compound is in an aerosol.
 37. The method of claim 35 wherein the treatment compound is in a gaseous state.
 38. A method of inhibiting pyrophoric activity of iron sulfides comprising contacting iron sulfides and/or precursors thereof with an effective inhibiting amount of a treatment compound in an aerosol or in a gaseous state to inhibit pyrophoric activity of the iron sulfides, said compound being amine, alcohol, ketone, or mixtures thereof.
 39. The method of claim 38 wherein the treatment compound is in an aerosol.
 40. The method of claim 39 wherein said amine comprises alkylamine, arylamine, and alkanolamine.
 41. The method of claim 38 wherein the treatment compound is in a gaseous state.
 42. The method of claim 41 wherein said amine comprises alkylamine, arylamine, and alkanolamine. 